This invention relates generally to gas turbine engines and methods for oil cooling in such engines.
Gas turbine engines are commonly provided with a circulating oil system for lubricating and cooling various engine components such as bearings, gearboxes, electrical generators, and the like. In operation the oil absorbs a substantial amount of heat that must be rejected to the external environment in order to maintain the oil at acceptable temperatures. As engine designs evolve the amount of heat to be rejected is increasing.
Known oil cooling systems for gas turbine engines typically include one or more air-to-oil heat exchangers, referred to as “air cooled oil coolers” or “ACOCs”, These heat exchangers can be heavy and have high drag, and can require special inlet and outlet ducts and large, heavy brackets. Sometimes ACOCs are used in series with fuel-to-oil heat exchangers and fuel return-to-tank systems (“FRTT”) in a complex cooling network; however increasing heat loads are expected to exceed the capabilities of such systems.
It has been proposed in the prior art to circulate fluid directly inside of flow-bounding structures such as outlet guide vanes (“OGVs”). But for flight critical fluids such as lubricating oil, a damaged heat exchanger is problematic as it could cause fires or critical loss of oil.
Accordingly, there is a need for a gas turbine engine heat exchanger having low drag, which allows the oil to be separated from the heat exchanger physically, while maintaining a strong thermal connection through the cooling cycle.